Mapping QTLs with additive effects and additive × additive epistatic interactions for harvest index in wheat (Triticum aestivum L.)

To map quantitative trait loci (QTL) for harvest index, 148 recombinant inbred lines and their parents, Yecora Rojo and an Iranian landrace line (No. 49), were evaluated under normal and terminal water deficit stress conditions in the research stations of Mahabad University and Miyandoab Agricultural Research Center, Iran, during 2014 and 2015. The experiment was carried out as design alpha lattice design with two replications. A linkage map of 51 retrotransposon and 177 microsatellite markers was used in this investigation. Quantitative trait loci (QTL) for additive effects and additive × additive interactions were determined by QTL Network 2.0 software using CIM and mixed-linear methods. QTL analysis revealed that under normal condition, six QTLs (R2A= 0.04 to 12.0%), two QTL × environment (E) interactions (R2AE= 6.28%), five additive × additive epistatic effects (R2AA= 0.7 to 8.68%) and 12 additive × additive × E (R2AAE= 3.76 to 11.4%) were significant. Under water deficit stress conditions, two QTLs (R2A= 5.0 to 7.0%), two additive × additive interactions (R2AA= 3.72 to 5.48%) and seven additive × additive × E interactions (R2AAE= 8.04 to 9.58) were identified. Among the eight QTLs identified, three QTLs were located on chromosome 2D, suggesting the importance of this chromosome in controlling harvest index, which may be used for marker assisted selection in breeding programs.